1. Field of Invention
The invention relates to an apparatus and a system of operation of a plurality of ion-exchange membranes. More specifically, the invention relates to an apparatus and system of operation of a plurality of electrodialysis membranes and gaskets stacked for separation of components from liquids passing through the membranes.
2. Description of the Related Art
Prior methods of treatment for separating polar components in liquid mixtures having contaminants have been utilized to purify water, to desalinate water, and to purify ethylene glycol or other mixtures of chemicals. One method utilizes ion exchange resins for separation of polar components on granular ion exchange resins, which require chemical regeneration of the resins and/or disposal of the resins. Another treatment method for separating polar components in liquid mixtures include micro-porous membranes which selectively allow smaller polar compounds to pass through the membrane, while denying passage of larger sized polar compounds. Another treatment method includes ion exchange membranes having anion and cation exchange membranes assembled in an alternating configuration in a unit of membranes.
Prior purifying and recycling devices include a plurality of ion exchange bipolar membranes separating solution compartments, and gasket separators secured together in face-to-face contact in a configuration of a multi-layered, stacked plate. The gasket separators between the membranes provide sealing at the edges of the stacked plate of membranes, and enable a fluid to flow into and out of the stacked plate and through the individual solution compartments between the stacked plate of membranes. The ion exchange bipolar membranes can contain an anode and a cathode electrode at the respective ends of the stack of membranes in order to provide an electrical input for maintaining a differential voltage between the anode end and the cathode end. When a direct current is passed through the multi-layered stacked plate, the ions contained in the solution to be purified will migrate in a direction in relation to the current depending on the charge of each ion in the solution. The cations move toward the cathode or negative electrode, while the anions move toward the anode or positive electrode. By controlling the electrical input, and therefore the differential voltages, an operator induces the movement of the cations and anions in different directions across the stack of membranes, thereby operating the purifying and recycling system to remove contaminants from ethylene glycol, water, and/or other liquid solutions.
At least three types and sizes of stacks of electrodialysis membrane units are utilized in prior purifying and recycling devices, including an electrodialysis concentration cell having a cation membrane, a dilution or feed compartment, an anion membrane, and a concentrate or product compartment which forms a unit utilized for desalinating of brine solutions. A second type of electrodialysis membrane unit includes a two-compartment cation cell having a bipolar membrane, a feed compartment, a cation membrane, and a base or product compartment. A third type of electrodialysis membrane unit includes a two-compartment anion cell having a bipolar membrane, a product compartment, an anion membrane, and a feed compartment. Additional types of electrodialysis membranes can include any combination of layers of the above three types to form a plurality of cation and anion membranes, interspersed with compartments and gaskets separating the compartments. Electrodialysis designs for flow through the stacks of electrodialysis membranes include sheet flow and tortuous flow. Sheet flow stacks induce liquid flow across the length or width of the active membrane surface area, and generally are utilized for low linear velocity conditions in the range of 5 to 10 cm/sec. Tortuous flow stacks induce liquids to take a long flow path around gaskets, and are utilized for higher linear flow velocity conditions in the range of 30 to 50 cm/sec.
Utilization of the electrodialysis designs as described above in stacks of membranes for purifying and recycling of ethylene glycol solutions, or for purifying water and desalinating water require a plurality of multiple membranes having complicated configurations. There is a need for a simplified design of a series of electrodialysis membranes in stacked configurations for improved removal efficiencies of contaminants in a purification and deionizing system.
Therefore, it is an object of the present invention to provide an improved membrane cell stack for purification of liquid mixtures.
It is another object of the present invention to provide a method of operation for an electrodialysis treatment system providing increased efficiency for ion-removal of liquid mixtures.
It is another object of the present invention to provide a membrane and gasket cell stack system having reduced assembly time.
It is another object of the present invention to provide a system having a plurality of membranes and interchangeable gaskets for improved efficiency for removal of contaminants by electrodialysis deionizing of liquid mixtures.
It is another object of the present invention to provide an improved system having a plurality of membranes and interchangeable gaskets for improved efficiency for deionizing liquid mixtures by an electrodialysis apparatus.